Automated soil measurement device

ABSTRACT

A filtration system for a soil analysis device and methods of pressure filtration and automated cleaning are disclosed for generating filtrate used in measuring characteristics of a soil sample and preparing the filtration system for repeated measurements. A mixing chamber combines a soil sample and an extractant into a liquid mixture. The filtration system receives and pressure filters the liquid mixture to quickly generate filtrate used to measure characteristics of the sample. The filtrate is passed to a measurement cell for analysis. Once the analysis is complete, the filtration system performs a cleaning process in preparation to receive a subsequent liquid mixture from another soil sample.

BENEFIT CLAIM/CROSS REFERENCES

This application claims the benefit as a continuation of U.S.application Ser. No. 13/794,331, filed Mar. 11, 2013, which claimspriority to U.S. Provisional Application No. 61/679,570, filed on Aug.3, 2012, the entire contents of both are hereby incorporated byreference for all purposes as if fully set forth herein. Theapplicant(s) hereby rescind any disclaimer of claim scope in the parentapplication(s) or the prosecution history thereof and advise the USPTOthat the claims in this application may be broader than any claim in theparent application(s).

BACKGROUND

1. Field of Art

The present invention generally relates to soil measurement and testing,and more specifically, filtration of a soil-extractant mixture.

2. Description of the Related Art

Nutrient levels in soil have significant spatial and temporalvariations. Accordingly, there has been significant effort placed intodevelopment of local nutrient management schemes, often referred to as“precision agriculture,” addressing nutrient level variation. Localnutrient management increases agricultural efficiency while reducing itsenvironmental impact by allowing growers to locally apply nutrientswhere needed. Increases in nutrient costs and a growing awareness of theenvironmental consequences of current agriculture practices have madeimprovements in agricultural efficiency and environmental impactincreasingly important.

For example, fertilizer inputs are a large fraction of agriculturalinput costs and prices of nutrient input have almost doubled in recentyears, increasing concern about future price fluctuations among growers.Meanwhile, in addition to long-standing concerns about the effect offertilizers on water quality, greenhouse gas emissions caused bynitrogen-based fertilizers have become an increasing concern. Forexample, it is estimated that N2O emissions caused by fertilizervolatilization are responsible for 5-10% of the forcing for globalwarming. Thus the ability to optimize the use of fertilizer inputs, andnitrogen-based fertilizers in particular, is increasingly recognized asa vital component of environmental sustainability. As a result of thesefactors, there is a rapidly growing interest in more efficient nutrientmanagement.

Local measurement of soil nutrient levels is a significant component oflocal nutrient management scheme. However, conventional methods forlocally measuring soil nutrient levels have limited the effectiveness ofexisting local nutrient management schemes. Conventionally, capturing anumber of samples/acre at the appropriate time to make effectivedecisions is often prohibitively time consuming and expensive. Forexample, lettuce growers in certain area typically plant several cropcycles each year, and have a five day window between harvesting andplanting the next crop. Logistically, this results in a very small timewindow, 1-2 days, in which to sample the field and apply fertilizer.This short time frame prevents use of standard laboratory-based soiltesting, which often takes 1-2 weeks to provide a result. Consequently,growers typically make decisions on fertilizer application based onhistorical analysis, instead of on current soil conditions.

As another example, in-season nitrogen management in corn-growingregions is often difficult because of the slow turnaround time oflaboratory-based soil testing. Extending the time when corn growers areable to measure soil nitrogen levels would allow corn growers to testfields before their last application of fertilizer. This enables corngrowers to test fields later in the growing season and implementnitrogen management practices. Further, allowing growers to promptlyretest fields, such as retesting after a rain, allows growers to adoptmore efficient nitrogen management practices. Additionally,laboratory-based soil measurement costs scale directly with the numberof samples, making it prohibitively expensive to sample at high griddensities. Thus, the development of a fast, simple, and inexpensive soilwould expand the benefits of precision agriculture.

Additionally, standard laboratory-based tests are relatively slow andexpensive. For example, a traditional laboratory-based test may use afiltration system that incorporates a filter that operates using theforce of gravity. For example, gravity acts on a liquid mixture togenerate filtrate for a measurement. This process is not only tediousbut requires frequent replacement of filters, ideally a new filter foreach sample processed. Labs may speed up these measurements by creatinga vacuum on the filtrate side of the filter to generate a negativepressure differential to increase the rate of filtrate generation. Suchmethods are often used in controlled lab environments with specializedand fragile lab equipment such as Buchner flasks with a vacuum pump andthe like. Such setups are impractical for use in the field.

Accordingly, there have thus been numerous efforts to develop variousother fast soil nutrient detection tools for use in the field.Technologies used include mid-infrared (mid-IR) spectroscopy,ion-selective electrodes, and chemical-reaction based strip tests.However, the use of each method has suffered from some combination ofexpense, low accuracy, stringent calibration requirements or difficultyof use.

Accordingly, a rapid and economical system for soil analysis that doesnot require a controlled lab environment could provide more accurate andtimely nutrient management recommendations which improve agriculturalefficiency.

SUMMARY

A soil analysis device provides the ability to process a soil sample andanalyze the processed soil sample to identify characteristics of thesoil sample. For example, a soil analysis device combines a soil samplewith an extractant, such as water, to produce a liquid mixture (orslurry). A portion of the slurry is exposed to a broad-band lightsource, with wavelengths varying from ultraviolet to visible tonear-infrared, to generate an attenuation spectrum identifying theattenuation of different wavelengths of the light by the slurry. Theattenuation spectrum is analyzed to determine characteristics of thesoil sample. For example, peaks in the attenuation spectrum are analyzedto identify nutrients present in the soil sample. Such measurementsprovide an ideal analysis of soil properties like nitrogenconcentration.

Embodiments of the soil analysis device described herein further providethe ability to process soil samples and perform such measurements with ahigh degree of accuracy and precision outside of a laboratoryenvironment, such as at an agriculture retailer's office or a mobiletrailer in the field. In one embodiment, the soil analysis devicecomprises a mixing chamber for generating the slurry, a filtrationsystem for filtering unwanted particulate from the slurry to generatefiltrate, and a measurement cell for analyzing the filtrate.

The speed of filtration and reliability in producing repeatable samplesof slurry for measurements may be increased through pressure filteringin a sealed, self cleaning filtration system. An embodiment of thefiltration system includes a slurry chamber for receiving the slurryfrom the mixing chamber. A filter separates the slurry chamber from afiltrate chamber and may be oriented in a substantially verticalorientation. Perforations in the filter allow filtered slurry (filtrate)to pass from the slurry chamber, through the perforations in the filter,into a filtrate chamber that collects filtrate for soil measurements.

To pressure filter a liquid mixture, the slurry chamber receives avolume of slurry from the mixing chamber sufficient to cover theperforations of the filter. In some embodiments, a valve coupled to theslurry chamber may release trapped air in the chamber as the liquidmixture is introduced. An air source pressurizes the slurry chamberwhich causes the filtration system to quickly generate a volume offiltrate by forcing the slurry through the filter. In other words,pressurization of the slurry chamber pressure filters the volume ofslurry at a greater rate than otherwise possible, until the perforationsare exposed and the pressure between the chambers is equalized.Depending on the embodiment, the air source may be coupled to the valve,utilize a second valve coupled to the slurry chamber, and/or pressurizethe liquid mixture within the mixing chamber coupled to the slurrychamber. Once enough filtrate is generated for a measurement, or ameasurement performed during filtration is complete, a drain of theslurry chamber may be opened to drain any remaining slurry.

In some embodiments, a compressor of the air source may be coupled tothe filtrate chamber to create a vacuum. The vacuum may be generated inthe filtrate chamber to evacuate air from the filter assembly In oneembodiment, the vacuum is generated in the filtrate chamber to evacuateair in the filter assembly. The evacuation of air aids in quicklyfilling the slurry chamber of the filtration system. Once the slurrychamber is filled, the vacuum may be turned off and pressure in theslurry chamber is used to push the liquid mixture through the filter tocreate filtrate. In alternate embodiments, the generator may remain onto pull slurry through the filter.

The filtrate chamber includes a filtrate drain to pass the filtrate intothe measurement cell. The measurement cell is coupled to a light sourceso that light propagating from the light source is attenuated by theliquid mixture in the measurement cell, and is measured by an opticaldetector that is also coupled to the measurement cell. The opticaldetector generates an attenuation spectrum indicating light received bythe detector at different wavelengths. The attenuation spectrum is usedto determine characteristics of the soil sample. In some embodiments,additional measurement devices are coupled to the filtration system toperform additional measurements of the characteristics of the soilsample.

Embodiments of the filtration system may also enable cleaning of thechambers and filter. A cleaner inlet coupled to the filtrate chamberintroduces a volume of cleaning fluid into the filtrate chamber. Topressure clean the filter, the filtrate chamber receives a volume ofcleaning fluid sufficient to cover the perforations of the filter. Anair source pressurizes the filtrate chamber which causes the filtrationsystem to force the cleaning fluid backwards (in a direction opposite offiltration) from the filtrate chamber through the filter into the slurrychamber. The backwards flow of cleaning fluid may dislodge particulatestuck in the filter. Cleaning fluid may also be introduced into theslurry chamber and passed through the filter in a process similar tothat for generating filtrate. The air source coupled to one or both ofthe chambers may be used to pass air through the chambers andmeasurement cell to dry the filtration system. The air drying my alsooccur in the forwards and backwards directions to ensure the filtrationsystem is fully dried in preparation for another measurement.

The features and advantages described in the specification are not allinclusive and, in particular, many additional features and advantageswill be apparent to one of ordinary skill in the art in view of thedrawings, specification, and claims. Moreover, it should be noted thatthe language used in the specification has been principally selected forreadability and instructional purposes, and may not have been selectedto delineate or circumscribe the inventive subject matter.

BRIEF DESCRIPTION OF DRAWINGS

Figure (FIG. 1 is a soil analysis device configured to create soilsample solutions and to self-clean between soil samples, according toone embodiment.

FIG. 2A is a side view of a filtration system for filtering a soilsample solution, according to one embodiment.

FIG. 2B is a front view of a filtration system for filtering a soilsample solution, according to one embodiment.

FIG. 3 is a flow chart of one embodiment of a method for generatingfiltrate from slurry using the filtration system in the soil analysisdevice.

FIG. 4 is a flow chart of one embodiment of a method for cleaning thefiltration system in the soil analysis device.

FIG. 5 is a high-level block diagram illustrating an example of acomputer for controlling a soil analysis device, according to oneembodiment.

FIG. 6 is a block diagram of a measurement cell for analyzing a soilsample solution, according to one embodiment.

FIG. 7 is a flow chart of a method for analyzing soil sample solutions,according to one embodiment.

FIG. 8 is a flow chart of a method for capturing multiple types ofmeasurements to determine soil composition, according to one embodiment.

STRUCTURE OF SOIL ANALYSIS DEVICE

Overview

FIG. 1 is a block diagram of one embodiment of a soil analysis device100. In one embodiment, the soil analysis device 100 includes a mixingchamber 110, a compressed air source 120, one or more cleaning fluidand/or extractant containers 130, a filtration system 140 and ameasurement cell 150. In an alternative embodiment, the measurement cell150 is absent and the device 100 comprises an output port (not shown)for apportioning out a filtered volume of solution for collection andtesting external to the device 100. The soil analysis device 100 alsoincludes a control system (not shown) for controlling the operation ofthe soil analysis device.

Generally, the mixing chamber 110 is configured to receive a field moistsoil sample and extractant, mix them together, and provide the mixedsolution (or slurry) to the filtration system 140. The filtration system140 filters the slurry and provides the filtered output either to themeasurement cell 150 for testing, or to the output port (not shown). Inone embodiment, the unfiltered slurry that is not filtered by thefiltration system 140 may also be supplied as a separate output. Thesoil analysis device 100 is further configured to use air from thecompressed air source 120 and a cleaning fluid from a container 130 toautomate self-cleaning of the mixing chamber 110, filtration system 140,and/or the measurement cell 150 or output port. Automated self-cleaningcleans the various components of the device 100 so that the measurementof later received soil samples is not tainted by previously receivedsoil samples.

The filtration system 140 filters the slurry to remove unwantedparticulate. Specifically, the filtration system 140 is configured toremove particulate that would otherwise interfere with the opticalmeasurement of the slurry by measurement cell 150. A benefit offiltering the slurry is that comparatively less dilution of the originalsoil sample by extractant is needed to achieve the same optical clarityif the slurry is filtered than if it is not. Less dilution of the soilsample improves the signal to noise ratio of optical measurementsperformed by measurement cell 150. Thus, filtering the slurry prior tomeasurement improves quality of the measurements made.

The measurement cell 150 includes a light source so that lightpropagating from the light source is attenuated by filtrate in themeasurement cell 150, and is measured by one or more optical detectorsthat are coupled to the measurement cell. The optical detectors generatean attenuation and/or a reflection spectrum indicating light received bythe detectors at different wavelengths. The attenuation and/orreflection spectrums are used to determine characteristics of the fieldmoist soil sample.

Filtration System

The filtration system 140 will now be described in more detail. Thefiltration system 140 includes a slurry inlet 124 coupled to a pipe 121for receiving the slurry from the mixing chamber 110. The pipe 121 isconfigured with a slurry inlet valve 122 to control flow of the slurryinto the filtration system 140. The slurry inlet valve 122 may be openedor closed in either a manual or automated fashion. In one embodiment,the slurry inlet valve 122 is a pinch valve. Pinch valves areadvantageous due to the soil component of the liquid mixture. The soilportions of the liquid mixtures may, through repeated use, clog valves,hindering their opening and closing motion thereby affecting the abilityto control the amount of liquid mixture that is transferred through pipe121. Pinch valves are less prone to clogging due to dirt than some othertypes of valves. In another embodiment, the slurry inlet valve 122 is aseated valve. Seated valves include a compliant stopper driven by anactuator, such as a piston. The actuator drives the compliant stopperagainst a seat to seal an opening of the valve 122 when the valve isclosed. In turn, the actuator pulls the compliant stopper away from theseat to allow liquid or slurry to flow freely through the opening of thevalve when the valve is opened. Seated valves are advantageous as thestopper and seat can be designed such that there exists a wide clearancein the open position, reducing the likelihood of clogs in the valve. Inone embodiment, the opening is around half an inch in diameter.

The slurry chamber 138 is separated from a filtrate chamber 142 by afilter 134. The filter 134 removes unwanted particulate from slurrypassing through it to generate filtrate in the filtrate chamber 142. Thesize of particulate filtered from the slurry may be adjusted based onthe porosity of the filter 134. For example, the pore sizes in thefilter may be set between 1-10 micrometers. In one embodiment, thefilter 134 is constructed of a material capable of reuse. For example,the filter 134 may be constructed from a porous metal sheet. As aspecific example, the filter 134 may be made of sintered, porous 316Lstainless steel with an average pore size between 1 and 5 micrometersand approximate thickness between 0.05 and 0.15 inches.

After the slurry chamber 138 is filled such that the porous filter 134surface is covered by slurry, the slurry inlet valve 122 controllingflow of slurry through the inlet 124 may be closed. As a result ofslurry passing through the filter 134 from the slurry chamber 138 intothe filtrate chamber 142, fine particulates may be left embedded in thefilter surface. This can have the effect of improving the efficiency ofthe filtration process beyond what would otherwise be possible for agiven average filter pore size.

Alternatively to using a reusable filter, the filter 134 may instead bea disposable filter (e.g., one time use), such as filter paper. Thefilter paper may be, for example, a specially designed filter paper cutto fit a frame of the filter 134.

Filtered slurry that has passed through the filter 134 (also referred toas filtrate) collects in the filtrate chamber 142. The filtrate chamber142 includes a filtrate drain 143 for feeding the measurement cell 150or otherwise collecting filtrate. The measurement cell 150 may includeits own separate drain, such that filtrate may flow from the filtratechamber 142, through the measurement cell 150 and subsequently flow outof the device 100. The filtrate drain 143 may include a valve (notshown) for controlling the flow of filtrate into the measurement cell150. For example, the valve may be adjusted to provide the analysisdevice 100 with the ability to measure soil nutrient concentrations(e.g., nitrate or nitrate-nitrogen) in the filtrate continuously, aswell as monitor when the filtration system 140 has run out of filtrateto measure. The valve may remain closed until a certain amount of timehas passed or a given volume of filtrate is collected in the filtratechamber 142 to prevent passage of air with filtrate into the measurementcell 150. Additionally, the valve may be adjusted to drain a portion ofinitial filtrate from the filtrate chamber 142 to prevent dirtier, earlyfiltrate from clouding and contaminating later, cleaner samples passingthrough the measurement cell 150.

The filtration system 140 may filter the slurry under pressure toincrease the speed of filtration and reliability of producing repeatablesamples of the slurry for measurement in the measurement cell 150. Theslurry is introduced to the slurry chamber 138 and impeded from flowinginto the filtrate chamber 142 by the filter 134. In order to increasethe speed at which filtrate is collected in the filtrate chamber 142,the slurry chamber 138 may be pressurized by a compressed air source 120to force the slurry against (and through) the filter 134. For example,the slurry chamber 138 may include a pressurization valve 126 coupledvia a pipe to the compressed air source 120. In some embodiments, thepressurization valve 126 may also include a pressure release to vent theslurry chamber 138 to atmosphere. Allowing the slurry chamber 138 tovent to atmosphere as slurry is introduced into the chamber may increaseflow rate of the slurry (i.e., by preventing backflow of air into themixing chamber), thus enabling the slurry chamber 138 to fill morequickly to reduce measurement time. The vent remains closed when thepressurization valve 126 is opened to pressurize the slurry chamber 138or the slurry chamber 138 is otherwise pressurized (e.g., in instanceswhere slurry is pressurized at the mixing chamber).

When the pressurization valve 126 is opened, the slurry in the slurrychamber 138 is pressurized by the compressed air source 120, forcing theslurry through the filter 134 to generate the filtrate at a greater ratethan otherwise possible. In this example, in addition to controlling theflow of the slurry, the slurry inlet valve 122 may be substantiallyairtight when closed or otherwise prevent backflow of slurry and/or airinto the mixing chamber 110 when the filtration system 140 ispressurized. In other embodiments, the slurry in the mixing chamber 110is pressurized by the compressed air source 120 to force slurry into theslurry chamber 138 via inlet 124 and through the filter 134.

In some embodiments, the compressed air source 120 may be used togenerate a vacuum in the filtrate chamber 142. The vacuum may be usedfor evacuating trapped air from the filter assembly to aid in allowingthe slurry chamber 138 to fill quickly and/or helping to pull the slurrythrough the filter 134. For example, the filtrate chamber 142 mayinclude a vacuum valve 128 coupled via a pipe to a compressor (notshown) of the compressed air source 120. Activating the compressor andopening the vacuum valve 128 creates a vacuum in the filtrate chamber142, thereby pulling slurry through the filter 134 in the filtratechamber 142. In one embodiment, the vacuum valve 128 is opened, with orwithout additional pressurization applied to the slurry chamber 138, toquickly generate an initial amount of filtrate in the filtrate chamber142 prior to passing filtrate through the filtrate drain 143. The vacuumvalve 128 may also include a pressure release to vent the filtratechamber 142 to atmosphere. Venting the filtrate chamber 142 toatmosphere can prevent backflow (i.e., the introduction of air bubblesto the filtrate) from the measurement cell 150 when the filtrate drain143 valve is opened.

The slurry chamber 138 may also include a slurry outlet 136 allowingremoval of the contents of the slurry chamber 138 in preparation for acleaning process and subsequent sample. The slurry outlet 136 mayinclude a valve (not shown) that may be opened or closed in either amanual or automated fashion to allow drainage of the contents of theslurry chamber 138, for example, after filtered slurry has been measuredin the measurement cell 150. In one embodiment, the outlet 136 may be anopening having a movable cover (not shown), so that moving the coverallows the contents of the slurry chamber 138 to drain. In eitherinstance, closing the valve or cover of the slurry outlet 136 preventsdrainage of the slurry from the slurry chamber 138 during filtration.

In some embodiments, the filtration system 140 is configured to enable aself-cleaning of the chambers 138, 142, filter 134 and measurement cell150. The cleaning process may be automated or performed manually. Asshown, filtrate chamber 138 includes a cleaner inlet 132 for receiving acleaning fluid, such as water, in the filtrate chamber 142. The cleanerinlet 132 is coupled to one of the containers 130 via a pipe (notshown). Alternatively, or in addition to receiving cleaning fluid viathe inlet 132, cleaning fluid may be received in the slurry chamber 138from the mixing chamber through pipe 121. In this case, cleaning fluidis passed from container 130, through the device 100, and into chamber138 when no slurry is present in the device 100. In some embodiments,the filtration system 140 utilizes the backwards flow of cleaning fluidthrough the filter 134 to remove embedded particulate in filter mediaduring the cleaning process. The slurry outlet 136 may be opened todrain cleaning fluids and excess slurry particulate from the filtrationsystem 140. In turn, the filtrate drain 143 may be opened to drain anycleaning fluid and filtrate. Passing cleaning fluid in this manner helpsdislodge particulate stuck in the filter 134 during slurry filtration,and helps flush excess slurry and filtrate present in the chambers 138,142 after a measurement has been conducted.

In a specific example, cleaning fluid introduced into the filtratechamber 138 may be passed backward through the filter 134 from chamber138 to chamber 142 and flushed from the slurry chamber 138 throughopening the slurry outlet 136. The slurry outlet 136 may, in turn, closeto allow cleaning fluid introduced via the inlet 132 to collect in theslurry chamber 138. The cleaning fluid in the slurry chamber 138 may bepassed forwards through the filter 134 from chamber 142 to chamber 138and flushed from the filtrate chamber 142 through the measurement cell150. Passing cleaning fluid both forward and backward through thefiltration system in this manner may improve the amount of left-overmaterial removed from the filtration system 140.

The filtration system 140 may also pressurize (or form a vacuum in) thechambers 138, 142 as needed to more forcefully pass cleaning fluidthrough the filter 134 in the backward and/or forward directions. Forexample, the filtration system 140 may pressurize (e.g., via valve 128)the filtrate chamber 142 using a compressor of the compressed air source120 to help pass cleaning fluid through the filter 134 into the slurrychamber 138. In turn, the slurry drain 136 may be opened to flush thecleaning fluid. Alternatively, or in addition to pressurizing thefiltrate chamber 142, the filtration system 140 may form a vacuum (e.g.,via valve 126) the slurry chamber 138 using the compressed air source120 to help pull cleaning fluid through the filter 134 and into theslurry chamber 138. The opposite steps may be taken to help clean thefilter 134 in the forward direction and the filtrate drain 143 opened toflush the cleaning fluid. Alternatively, the cleaning fluid in thefiltrate chamber 142 may be passed back through the filter 134 into theslurry chamber 138 to drain.

The compressed air source 120 may also be used to dry the chambers 138,142, filter 134 and measurement cell 150. Similar to the flow ofcleaning fluid through the filtration system 140, air may be passed in aforwards and backwards direction through the filter 134. To pass air ina given direction (e.g., forward) through the filter 134, one chamber(e.g., 138) is pressurized and an outlet (e.g., filtrate drain 143) ofthe other chamber is opened. Subsequently forming a vacuum in the samechamber 138 or pressurizing the other chamber 142 and opening the slurryoutlet 136 may be used to pass air in the other direction. These stepseliminate any leftover soil sample and cleaning fluid from thefiltration device 140 in preparation to receive a new sample.

Example Filtration System

FIG. 2A is a side view of a filtration system 140 for filtering a soilsample solution, according to one embodiment. As shown, the filtrationsystem 140 includes a filter 234 partitioning a slurry chamber 238 and afiltrate chamber 242. Additionally, as described with reference to FIG.1, the slurry chamber 238 and/or filtrate chamber 242 may include valves(not shown for clarity) coupled to a compressed air source 120 forpressurizing and/or vacuuming the chambers during filtration andcleaning. In the depicted embodiment, the filtration system 140 isoriented vertically, with ground being located parallel with the bottomof the figure. Consequently, gravity acts as a downward force along thevertical axis of the depicted figure. In other embodiments, thefiltration system 140 may be oriented in other directions and will stillfunction similarly.

The slurry chamber 238 is coupled to a slurry inlet 224 at its top and aslurry drain 236 at its bottom. The size of the slurry inlet 224 anddrain 236 may be configured as desired to a diameter sufficient to allowthe slurry to flow into and out of the chamber, preferably withoutclogging. The assembly of the slurry drain 236 may include a valve 240that is actuated manually, or automatically, to open and seal the drain236. The slurry chamber 138 may also include a vent valve (not shown)for venting the chamber 138 to atmosphere, allowing trapped air in thechamber to escape while filling the chamber.

The filtrate chamber 242 is coupled to a cleaner inlet 232 at its topand a filtrate drain 243 at its bottom. The filtrate drain 243 mayinclude an assembly (not shown) with a valve (e.g., of different scale,but functionally similar to that of valve 240) to control the flow offiltrate collected in the filtrate chamber 242 to a measurement cell(not shown). The filtrate drain 243 may be a smaller size than theslurry drain 236 as the filter 234 removes clogging particulate and tobetter control the flow of filtrate into the measurement cell.

For scale, in one embodiment, the filtration system 140 is about 0.5-4inches in depth and 9-21 inches tall and about 3-7 inches wide toprovide a large, vertical filter 234 surface area. In one embodiment,the height-width ratio is approximately 3:1. The filter 234 itself maybe approximately the same dimensions, with the perforations/perforatedarea configured as described below. The filter 234 may also be larger orsmaller. The filter 234 may be sandwiched between a front plate formingthe filtrate chamber 242 and a black plate forming the slurry chamber238 which are all held together using a number of fasteners 260.Compressible seals (not shown) such as a gasket or o-ring may run thelength of the junctions between the surfaces of the filter 234, the backplate forming the slurry chamber 238, and/or the front plate formingfiltrate chamber 242 to prevent air/slurry leakage between the chambersand filter. In an alternate embodiment, the front plate and back platemay be constructed as a single piece (or affixed) with a slit at the topfor the filter 234 to slide into to form the slurry and filtratechambers.

As described previously, embodiments of the filter 234 may include anumber of perforations 210 (not shown to scale) that allow slurry topass through the filter 234. The perforations cover at a portion of thesurface area of the filter 234 up to a slurry line 220. The slurry fillline 220 indicates the volume of slurry in the slurry chamber 238 thatcovers the perforations 210. If the slurry chamber 238 is filled to thisline, the slurry chamber can be pressurized and/or a vacuum formed inthe filtrate chamber 242 to assist with filtrate creation. Similarly, iffilled with cleaning fluid at or above this line 220 in a given chamber238 or 242, the given chamber can be can be pressurized and/or the otherhave a vacuum formed therein to help clean the filter 234 during acleaning sequence. Once the slurry volume falls below the fill line 220,air will flow from the slurry chamber 238 to the filtrate chamber 242through the filter 234 perforations 210, thus equalizing the pressure.

In a specific embodiment, the perforations 210 may extend the width ofthe filter and vertically from a filtrate fill line 230 to a slurry fillline 220. As larger particulate typically collects at the bottom of theslurry chamber 238, the portion of the filter 234 below the filtratefill line 230 may not include any perforations as its contribution tofiltrate generation may be minimal. Additionally, provided the volume offiltrate in the filtrate chamber 242 at the filtrate fill line 230 issufficient for providing a measurement reading, the slurry drain valve240 may be opened to begin draining the slurry chamber 238.

Other embodiments may includes filters 234 where the perforations 210extend from the slurry fill line 220 to the bottom of chambers 238 and242. Additionally, in embodiments where cleaning fluid and slurry arepressurized in the container 130 and mixing chamber 110, respectively,the perforations may extend to the top of the filter 134 rather than theslurry fill line 220.

By orienting the filter surface vertically, cleaning and drying of thefilter 234 is made easier, however alternate embodiments may have thefilter in a horizontal orientation, which may reduce the tendency forthe filtrate to contain bubbles. Other implementations used cylindricalfilters with the slurry chamber formed on the inside of the cylinder andthe filtrate chamber on the outside or vice versa. One skilled in theart will recognize the configuration of the inlets 224, 232, drains 236,243, and filter 234 may deviate from the embodiment shown in FIG. 2A toaccommodate these alternate embodiments.

A table 1 illustrating example combinations for passing filtrate,cleaning fluid, and/or air through the filter and filtration system areshown for reference:

TABLE 1 Chamber Fluid Pressure Vacuum Inlets/Outlets Result Slurry 238Slurry in Y N Drain 236 Closed Generate Filtrate chamber 238 Filtrate242 Slurry in N Y Drain 243 Closed Generate Filtrate chamber 238Filtrate 242 Slurry in N N Drain 243 Open Pass Filtrate chamber 238 toCell 150 Slurry 238 Cleaner in Y N Drain 236 Closed, Pass Cleanerchamber 238 Drain 243 Open Forward & Drain Slurry 238 Cleaner in N YDrain 236 Closed Pass Cleaning chamber 242 Fluid Backward Filtrate 242Cleaner in N Y Drain 243 Closed Pass Cleaning chamber 238 Fluid ForwardFiltrate 242 Cleaner in Y N Drain 243 Closed, Pass Cleaner chamber 242Drain 236 Open Backward & Drain Slurry 238 Air Y N Drain 236 Closed,Pass Air Forward Drain 243 Open Slurry 238 Air N Y Drain 236 Closed,Pass Air Backward Drain 243 Open Filtrate 242 Air Y N Drain 243 Closed,Pass Air Backward Drain 236 Open Filtrate 242 Air N Y Drain 243 Closed,Pass Air Forward Drain 236 OpenSome embodiments may utilize more than one combination at once, forexample, the slurry chamber 238 may be pressurized and the filtratechamber 242 under vacuum at the same time and vice verse. Additionally,the use of pressurization and/or vacuum during any given step forgenerating filtrate or passing of cleaning fluid may be optional, forexample, if a sample is gravity filtered or the system does not includea vacuum. Some combinations may include operation of additional or lesshardware depending on the embodiment.

FIG. 2B is a front view 201 of a filtration system 140 corresponding tothe example embodiment illustrated in FIG. 2A for filtering a soilsample solution, according to one embodiment. The side view cut A,illustrated in FIG. 2A, is shown for reference.

The perforations 210 of the filter 234 extend across the width of thefilter and vertically from the slurry fill line 220 to the filtrate fillline 230. The bottom portion of the chambers may be formed as a trough250 for guiding the filtrate/slurry to the bottom of the respectivechambers and out the filtrate drain 243 and slurry drain 236.

Slurry Filtration

FIG. 3 is a flow chart of one embodiment of a method 300 for generatingfiltrate from slurry using the filtration system 140 in the soilanalysis device 100. In the embodiment shown by FIG. 3, the slurrychamber 138 receives a liquid mixture (or slurry) comprising a portionof a soil sample mixed with an extractant such as water and optionally asalt.

The slurry inlet valve 122 remains open for at least a first durationsufficient to ensure 320 slurry coverage of the filter 134. The slurryinlet valve 122 may also remain open for a further second durationsufficient to introduce an additional volume of slurry into the slurrychamber 138 after some slurry has already filtered through the filter134 in order to generate enough filtrate to perform a measurement.

Once enough slurry is collected in the slurry chamber 138, the inletvalve 122 may be closed to seal the chamber in instances where theslurry chamber 138 is pressurized 330 through opening of the slurrypressurization valve 126 at the top of the chamber. In alternateembodiments where the slurry itself introduced into the chamber 138under pressure (e.g., when the slurry is pressurized in the mixingchamber), the inlet valve 122 may remain open until filtrationconcludes. In either instance, the slurry chamber 138 is pressurized byway of the slurry in the chamber covering the filter to create apressure differential between the chambers (across the filter) toaccelerate the generation 340 of filtrate in the filtrate chamber 142.

In some embodiments, the filtrate chamber 142 includes a vacuum valve128 for generating a vacuum in the filtrate chamber 142 to pull air outof the filter chamber to aid in filling the slurry chamber 138 and/or tohelp pull slurry through the filter 134 during pressure filtration at agreater rate than otherwise possible. The vacuum valve 128 may be usedfor a given duration in a pre-measurement stage to quickly generate 340an initial volume of filtrate prior to filtrate being allowed to enter ameasurement cell 150. In order to prevent backflow from the measurementcell 150, the filtrate drain 143 remains closed while the vacuum valve128 is open and/or a vacuum persists in the filtrate chamber 143. Afterthe duration of the pre-measurement stage, the vacuum valve 128 ventsthe filtrate chamber 142 (e.g., to atmosphere) prior to opening of thefiltrate drain 143.

The filtrate drain 143 is opened to drain 350 filtrate collected in thefiltrate chamber through the measurement cell 150. The filtrate drain143 may regulate the flow of filtrate to ensure that enough filtrateflows through the measurement cell 150 throughout a reading periodwithout depleting the volume of filtrate collected in the filtratechamber 142. Depleting the filtrate chamber 142 may introduce unwantedgases into the measurement cell 150 and provide an inaccurate reading.

The measurement cell 150 may sense 360 completion of filtration throughthe detection of gasses in the filtrate. Specifically, the measurementcell 150 may halt filtration based on the measured absorbance spectra offiltrate including a significant proportion of air rather than sample.Alternatively, the measurement cell 150 may sense 360 completion of ameasurement (e.g., due to a stable reading) of the filtrate prior todetection of the change in absorbance spectra due to the presence of air(e.g., prior to generating the entire volume of filtrate). In eitherinstance, the slurry drain 136 and/or filtrate drain 143 may be openedto pass excess slurry/filtrate from the filtration system 140.Optionally, the pressurization valve 126 may be closed at this stage. Inan alternative embodiment, filtration may be stopped after a particularperiod of time or responsive to a user input to cease filtration.

In some embodiments, the entire volume of filtrate may be generated 340prior to a measurement or for collection in a vessel for a latermeasurement. In turn, the vacuum valve 128, in addition to thepressurization valve 126, may remain open to create the vacuum until thedesired volume of filtrate is generated in the filtrate chamber 142. Forthis example, sensing 360 of the completion of filtration may occurprior to venting of the filtrate chamber 142 and subsequent opening ofthe filtrate drain 143 to drain 350 filtrate to prevent backflow fromthe vessel or measurement cell. Additionally, depending on theembodiment of the filtration system 140, opening of the slurry drain 136may have to wait until the collected filtrate is drained from thefiltrate chamber 142.

Filtration System Cleaning Cycle

FIG. 4 is a flow chart of one embodiment of a method 400 for cleaningthe filtration system 140 in the soil analysis device 100. In theembodiment shown by FIG. 4, the cleaning cycle 400 may optionally beinitiated once completion of filtration 360 is sensed or alternatively,prior to performing a measurement.

Prior to cleaning or as an initial step in the cleaning process, theslurry drain 136 and filtrate drain 143 may be opened to drain anyslurry/filtrate in the chambers 138, 142 of the filtration system 140.Additionally, a drain of the measurement cell 150 may be opened to passexcess filtrate received from the filtrate chamber 142 through the cell.

To clean a backward direction through the filter 134 (starting at thecircle labeled as 1 in FIG. 4), the filtration system 140 receives 410 acleaning fluid, such as water, in the filtrate chamber 142 through thecleaner inlet 132. The filtrate drain 143 may be closed in order to moreeasily fill the filtrate chamber 142 to the top of the filter 134. Incontrast, the slurry drain 136 is opened to drain any cleaning fluidpassed through the filter 134 from the filtrate chamber 142.

Accordingly, the filter system 140 feeds 420A the cleaning fluid throughthe filter 134 from the filtrate chamber 142 to the slurry chamber 138.Ideally, the feeding 420A of cleaning fluid in this direction (i.e.,backwards through the filter) dislodges particulate caught in the filter134 such that it flows out the slurry drain 136. After a desiredduration of cleaning, the filtration system 140 stops the influx 410 ofcleaning fluid in the filtrate chamber 142 and allows the slurry chamber138 to drain 430A the cleaning fluid and dislodged particulate.

In some embodiments, the chambers 138, 142 may be vacuumed and/orpressurized during the backwards cleaning phase (1) to pass cleaningfluid through the filter 134 with greater force to dislodge particulate.In the case of creating a vacuum in the slurry chamber 138, in oneembodiment, the slurry drain 136 and slurry inlet 124 remain closed anda valve coupled to a compressor of the compressed air source 120 isopened. In the case of pressurizing the filtrate chamber 142, cleaningfluid under pressure is received from container 130 via inlet 132 or thechamber 142 is pressurized via a valve coupled to the compressed airsource 120. In either case, the filtration system 140 receivessufficient cleaning fluid to ensure that the cleaning fluid covers thefilter 134.

To clean in a forward direction through the filter 134 (starting at thecircle labeled as 2 in FIG. 4), the filtration system 140 receives 411 acleaning fluid in the slurry chamber 132 through the slurry inlet 124.The slurry drain 136 may be closed in order to more easily fill theslurry chamber 138 to the top of the filter 134. In contrast, thefiltrate drain 143 is opened to drain any cleaning fluid passed throughthe filter 134 from the slurry chamber.

Accordingly, the filter system 140 feeds 420B the cleaning fluid throughthe filter 134 from the slurry chamber 138 to the filtrate chamber 142.After a desired duration of cleaning, the filtration system 140 stopsthe influx 411 of cleaning fluid in the slurry chamber 138 and allowsthe filtrate chamber 142 to drain 430B the cleaning fluid.

In some embodiments, the chambers 138, 142 may be pressurized and/orvacuumed during the reverse cleaning phase (2) to pass cleaning fluidthrough the filter 134 with greater force. In the case of creating avacuum in the filtrate chamber 138, in one embodiment, the cleaner inlet132 and filtrate drain 142 remain closed and the vacuum valve 128 isopened. In the case of pressurizing the slurry chamber 138, cleaningfluid under pressure is received from the mixing chamber 110 via inlet124 or the chamber 142 is pressurized via pressurization valve 126. Ineither case, the filtration system 140 ensures that the cleaning fluidcovers the filter 134. As described above, the filter 134 may be cleanedin both the forward and reverse directions in order to remove as muchparticulate as possible from the filter 134. Although described above ascleaning in the forward direction followed by cleaning in the reversedirection, the order of these operations may be reversed in anotherembodiment.

Subsequently to both forward and reverse cleaning with a cleaning fluid,the filter system 140 is air dried to remove any leftover cleaning fluidas well as to ideally flush any remaining particulate. At this stage,both drains 136, 143 are opened and the chambers are allowed to dry 440.Pressurized air from compressed air source 120 may also be blown intoone or more of the chambers 138, 142 to hasten the drying process. Aswith the reverse (1) and forward (2) cleaning fluid process describedabove, pressurized air cleaning may also be performed in a forward andreverse manner, in either order. This may be accomplished, for example,by opening and closing the valves, inlets, and outlets of the filtrationsystem 140 in a similar manner as described above.

Soil Analysis Device Operation

FIG. 5 is a high-level block diagram illustrating an example of acomputer 500 for use in controlling the operation of the soil analysisdevice 100, according to one embodiment. For example, the computercontrol system 500 may be used to control the opening and closings ofthe various valves, lids, and chambers of the filtration system 140,control the compressed air source 120 and compressor, and therebycontrol the motion of soil samples, filtrate, air, and cleaning fluidthrough the soil analysis 100 device in general, and through thefiltration system 140 particularly.

Illustrated are at least one processor 502 coupled to a chipset 504. Thechipset 504 includes a memory controller hub 520 and an input/output(I/O) controller hub 522. A memory 506 and a graphics adapter 512 arecoupled to the memory controller hub 520, and a display device 518 iscoupled to the graphics adapter 512. A storage device 508, keyboard 510,pointing device 514, and network adapter 516 are coupled to the I/Ocontroller hub 522. A code scanner (e.g., a barcode scanner or RFIDscanner, not shown) can also be coupled to the I/O controller hub 522.Other embodiments of the computer 500 have different architectures. Forexample, the memory 506 is directly coupled to the processor 502 in someembodiments.

The storage device 508 includes one or more non-transitorycomputer-readable storage media such as a hard drive, compact diskread-only memory (CD-ROM), DVD, or a solid-state memory device. Thememory 506 holds instructions and data used by the processor 502. Thepointing device 514 is used in combination with the keyboard 510 toinput data into the computer system 500. The code scanner (not shown) isused to input data into the computer system 500. The graphics adapter512 displays images and other information on the display device 518. Insome embodiments, the display device 518 includes a touch screencapability for receiving user input and selections. The network adapter516 couples the computer system 500 to an external network (e.g., alocal area network, a wireless network, or the internet). Someembodiments of the computer 500 have different and/or other componentsthan those shown in FIG. 5.

The computer 500 is adapted to execute computer program instructions forcontrolling the operation of the soil analysis 100. Instructions can beimplemented in hardware, firmware, and/or software. In one embodiment,executable computer program instructions are stored on the storagedevice 508, loaded into the memory 506, and executed by the processor502.

Measurement Cell

FIG. 6 is a block diagram of a measurement cell for analyzing a soilsample solution, according to one embodiment. The measurement cell 150is configured to optically measure characteristics of the soil samplesolution received from the filtration system 140. The measurement cell150 includes or is coupled to an input port 153 for receiving the soilsample solution, a cavity 154, one or more windows 155, 156, an opticalsource 152, one or more optical detectors 151 a, 151 b, and an outputport 157.

The optical source 152 initiates the measurement of the characteristicsof the soil sample solution by passing light through the received soilsample solution. A detector 151 a is placed opposite from the opticalsource 152 across the cavity 154, to capture an attenuation spectrum ofthe light passing through the soil sample solution as a function ofwavelength. In one embodiment, detectors 151 are spectrometers having a1 to 4 nanometer resolution. The detectors 151 have a sufficientsensitivity to allow detection of light passing through materials havinga high absorbance. This allows the detectors 151 to determine anattenuation spectrum associated with a soil sample solution bydetermining how different wavelengths of light are attenuated by thesoil sample solution present in the cavity 154.

In one embodiment, a second detector 151 b is placed on the same side ofthe cavity 154 as the light source 152, in order to obtain a reflectionspectrum of the light reflected from the soil sample solution. Thereflection spectrum may be used to determine characteristics of the soilsample.

Peaks in the attenuation spectrum allow identification of components ofthe soil. For example, attenuation peaks at wavelengths of approximately200 nanometers and 300 nanometers indicate nitrate-nitrogen in the soil.Similarly, attenuation peaks at wavelengths of approximately 210nanometers, 230 nanometers and 250-300 nanometers may be used toidentify nitrite-nitrogen, bisulfide and organic carbon, respectively,in the soil. Other peaks in the attenuation spectrum may also be used toidentify additional components of the soil. Additionally, if the soilsample solution contains chemicals in addition to soil and extractant,additional attributes of the soil in a sample may be determined from theeffect of the chemicals on the attenuation spectrum. For example, if thesoil sample solution includes a pH indicator, data captured by thedetector 151 a may be used to monitor the pH indicator and ascertainsoil pH. As another example, the soil sample solution may include acidsand/or reagents to enable the detector 151 a to measure the amount ofphosphorous or potassium in the soil.

In one embodiment, the light source 152 comprises a dualultraviolet-visible/near-infrared light bulb, such as a dualtungsten-deuterium bulb. The light source 152 allows independent controlof the production of ultraviolet light, visible light and near-infraredlight. For example, modification of a tungsten filament in the lightsource 152 modifies production of light having wavelengths of 320nanometers or longer (“visible light” and “near-infrared light”), whilemodification of a deuterium filament in the light source 152 modifiesproduction of light having wavelengths shorter than 400 nanometers(“ultraviolet light” or “UV light”).

The light source 152 may include a light source holder (not shown)connected to the window 156, where the light source holder includes anopening enabling the coupling of light (either by an optical fiber or byfree-space optics) to the window 156. For example, an optical fiberinserted into the opening in the light source holder directs light fromthe light source 152 through the optical fiber to the window 156.

Light emitted from the light source 152 travels an optical path lengthfrom the window 156 covering light source 152 to the window 155 coveringdetector 151 a. The optical path length affects the amount of lightcaptured by a detector 151. Thus, modifying the distance between window156 and window 155 affects the amount of visible or ultraviolet lightabsorbed by the soil sample solution in the measurement cell. In oneembodiment, the optical path length between windows 156 and 155 is onemillimeter.

Windows 156 and 155 isolate the source 152 and detectors 151 from thesoil sample solution present in the cavity 154. Windows 156 and 155 havea high transmission of infrared, ultraviolet and visible light. Forexample, windows 156 and 155 may include quartz or fused-silica windows.In one embodiment, the windows 156 and 155 include a hydrophilic film,such as a film of silicon dioxide, to reduce the likelihood of airbubbles developing near the windows. Alternatively the windows 156 and155 are made from a hydrophilic material. In one embodiment, the windows156 and 155 include a non-stick coating such as a TEFLON coating.

In one embodiment, cavity 154 is sloped in order to prevent theoccurrence of surface effects on windows 156 and 155. The cavity 154may, for example, be slanted (e.g., angled) or curved. The slopemitigates the kinetic energy of the soil sample solution that has beenfiltered by the filtration system 140, thereby inhibiting the creationof surface effects on windows 156 and 155. As a consequence, windows 156and 155 are more likely to be uniformly covered by a soil samplesolution. This improves the optical measurement of soil characteristics,by creating a more consistent optical path for light that is transmittedor reflected by the soil sample solution.

The measurement cell 150 additionally includes an output port 157 forclearing the contents of the measurement cell 150. The output port 157may additionally be used to input cleaning fluid to provide backpressureto clean the measurement cell 150 and/or the filtration system 140. Toperform cleaning, the output port 157 may be coupled to a pneumaticpiston or a solenoid valve.

In one embodiment, the soil analysis device 100 may includes a number ofmeasurement cells 150 allowing the measurement of differentcharacteristics of the soil sample simultaneously. For example, a secondmeasurement cell may be used to measure soil pH concurrently with themeasurement of other soil nutrients.

In addition to measurements performed by the measurement cell 150, thesoil analysis device 100 may also include additional measurement devicesin mixing chamber 110 for performing further measurements of the soilsample. Examples of measurement devices include a conductivity probe, aglass pH electrode, and ion selective electrodes including membranes formeasuring various nutrients such as nitrate and potassium. Theadditional measurement devices may also determine a moisture content ofa soil sample, a viscosity of the soil sample or the soil samplesolution, the temperature of the soil sample or the soil samplesolution, or any other suitable characteristics of the soil sample orthe soil sample solution. The data determined by the additionalmeasurement devices may be combined with the attenuation spectrumdetermined by the detector 151 to increase the accuracy of nutrientidentification in the soil sample. For example, determining the moisturecontent of the soil sample allows improvement of a nitrate-nitrogenmeasurement by subtracting the weight of moisture in the soil samplefrom the weight of the soil sample. In one embodiment, an additionalmeasurement device captures optical reflectivity measurements of thesoil in the mixing chamber 110, before extractant mixing, in the UV,visible, near IR and/or mid IR spectra. The reflectivity of dry soil asa function of wavelength may be correlated to soil type. Suchinformation can be used, in conjunction with the other embodimentsdiscussed herein to provide data about soil characteristics or to refinethe measurement of soil characteristics in the measurement cell 150.

The soil analysis device 100 allows for near real-time analysis of soilcomponents by integrating mixing of a soil sample and extractant withanalysis of the resulting soil sample solution. For example, the soilmeasurement of interest is often a final value after all relevantnutrients in the soil have been extracted from the soil sample solution,which may take a significant amount of time. By integrating a high-speedmeasurement (typically less than 1 second per measurement) measurementcell 150 and coupling it to the mixing chamber 110, the measurement canbe performed by the measurement cell 150 many times as the nutrient isbeing extracted and as the soil sample solution filters through thefiltration system 140, allowing the final value of the nutrient to beaccurately extrapolated in a much shorter amount of time. In contrast,conventional techniques of soil measurement are time-intensive becausethey rely on discrete steps of pre-processing the soil, extractingnutrients and then measuring nutrients, preventing these conventionalmethods from obtaining multiple measurements of soil characteristicsduring the measurement process.

The flow through rate of the filtration system 140 may be slow enoughthat air bubbles may occasionally become trapped in between drops ofsoil sample solution arriving in the measurement cell 150 from thefiltration system 140. The air bubbles cause the filtering soil samplesolution to become backed up, and can alter measurements of the soilsample solution. To prevent this, in one embodiment the measurement cell150 includes an overflow line (not shown) before the cavity 154. Theoverflow line allows trapped air bubbles to escape, allowing filteredsoil sample solution to take their place instead. The overflow line ispositioned proximately to the filtration system 140 above, vertically,the measurement cell 150 to allow the air to escape.

The overflow line also provides a place where filtered soil samplesolution may go once the measurement cell 150 has filled with filteredsoil sample solution. The overflow line thus removes excess filteredsoil sample solution that is not needed for measurement.

In an alternative embodiment, the shape of the measurement cell 150 maybe modified into a “V” shape by adding an upward sloping overflow lineat the bottom point of the cavity 154. In this embodiment, the overflowline slopes in a different direction than the input to cavity 154,forming the V-shape. The second portion of the V-shape is formed by theoverflow line, allowing trapped air bubbles and excess filtered soilsample solution to escape from the measurement cell 150. In thisembodiment, the other elements of the measurement cell 150 such as thelight source 152, detector(s) 151, and windows 156 and 155 may belocated out-of-plane from the V-shape. The output port 157 may belocated at the bottom of the V-shape next to cavity 154.

Measurement of Soil Characteristics

FIG. 7 is a flow chart of one embodiment of a method 700 for measuringdata describing soil composition using the soil analysis device 100. Inthe embodiment shown by FIG. 6, the mixing chamber 110 receives 710 asoil sample having a known weight and moisture content. The mixingchamber 110 also receives 720 an extractant. In one embodiment, a volumeor weight of extractant is received 720 based on the weight and moisturecontent of the soil sample to provide a desired ratio of soil toextractant. The mixing chamber 110 may also receive a salt to act as aflocculent on the soil sample.

The contents of the mixing chamber 110 are mixed to create 730 a soilsample solution. A portion of the soil sample solution flows from themixing chamber 110 into filtration system 140. The filtration system 140filters 740 the soil sample solution to remove soil particulates,organic matter, and other soluble organic materials from the soil samplesolution. For example, the filtration system 140 may perform the stepsdescribed with reference to FIGS. 3 and 4 to pressure filter the soilsample solution (slurry) to generate filtrate for analysis. The filteredsoil sample solution enters measurement cell 150.

Once in the measurement cell 150, the filtered soil sample solution isanalyzed 750 to determine the characteristics of the soil sample. In oneembodiment, ultraviolet, visible, and/or near-infrared light areincident upon and at least partially absorbed by the soil samplesolution. An attenuation spectrum is measured that provides dataregarding how the soil sample solution absorbs different wavelengths oflight. Peaks in the attenuation spectrum associated with the soil samplesolution allow identification of nutrients, or other components, in thesoil sample. A reflection spectrum may also be measured using the lightreflected from the soil sample in the measurement cell 150. Aftermeasurement, soil analysis device 100 is cleaned 760 to remove the soilsample solution from the mixing chamber 110, filtration system 140,and/or measurement cell 150.

FIG. 8 is a flow chart of one embodiment of a method for analyzing 750multiple characteristics of a soil sample solution to determine soilsample characteristics. In one embodiment, one or more additionalmeasurement cells 150 are coupled to the mixing chamber 110 and measurevarious characteristics of a soil sample solution. In one embodiment,measurement cell 150 and one or more additional measurement devicesmeasure various characteristics of the soil sample and the soil samplesolution. In one embodiment, measurements of various characteristics ofthe soil sample solution are measured in a single measurement cell 150,where the contents of the measurement cell 150 may change betweenmeasurements for a single soil sample. For example, the soil toextractant ratio may be changed through the addition of additionalextractant between measurements, or additional chemicals may be added toperform additional measurements.

In one embodiment, a thermal measurement device determines 810 atemperature of a portion of the soil sample solution. A power detectordetermines 820 a viscosity of the soil sample solution by measuring thepower consumed by the motor in mixing chamber 110 to reach a specifiedspeed, or by measuring the speed of the motor when a fixed amount ofpower is applied to the motor. In one embodiment, the measurement cell150 is used to determine 830 an absorption and/or a reflection spectrumof the soil sample solution. In one embodiment an additional measurementdevice or an additional measurement cell 150 in conjunction with anadded chemical determines 840 the pH of the soil.

The temperature, viscosity, attenuation spectrum and pH representcharacteristics of the soil. These measurements may also be analyzed todetermine other characteristics of the soil that were not directlymeasured. For example, the temperature, viscosity, attenuation spectrumand pH may be communicated from the soil analysis device 110 to aprocessor or computing device (not shown) which determines 850 thenutrients present in the soil sample. The measured and determinedcharacteristics of the soil sample are stored 860 in a memory and/ordisplayed to a user.

In one embodiment, the soil analysis device 100 is used in conjunctionwith a process for measuring soil characteristics as described in U.S.patent application Ser. No. 13/231,701, filed on Sep. 13, 2011, thesubject matter of which is incorporated herein by reference in itsentirety.

Hence, the disclosed soil analysis device 100 improves the accuracy ofidentifying nutrients in a soil sample while also increasing the speedwith which the nutrients included in a soil sample are identified.

Additional Considerations

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. It should be understood thatthese terms are not intended as synonyms for each other. For example,some embodiments may be described using the term “connected” to indicatethat two or more elements are in direct physical or electrical contactwith each other. In another example, some embodiments may be describedusing the term “coupled” to indicate that two or more elements are indirect physical or electrical contact. The term “coupled,” however, mayalso mean that two or more elements are not in direct contact with eachother, but yet still co-operate or interact with each other. Theembodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the invention. This is done merely for convenience andto give a general sense of the invention. This description should beread to include one or at least one and the singular also includes theplural unless it is obvious that it is meant otherwise.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs for asystem and a method for automatically identifying characteristics of thecomposition of a soil sample through the disclosed principles herein.Thus, while particular embodiments and applications have beenillustrated and described, it is to be understood that the presentinvention is not limited to the precise construction and componentsdisclosed herein and that various modifications, changes and variationswhich will be apparent to those skilled in the art may be made in thearrangement, operation and details of the method and apparatus of thepresent invention disclosed herein without departing from the spirit andscope of the invention as defined in the appended claims.

What is claimed is:
 1. A filtration system of a soil analysis devicecomprising: a first chamber; a mixing chamber coupled to the firstchamber for providing a liquid mixture to the first chamber; a filtercoupled to the first chamber for receiving the liquid mixture from thefirst chamber and for removing particulates from the liquid mixture togenerate a filtered liquid mixture; a measurement cell for analyzing thefiltered liquid mixture; a second chamber coupled to the filter forreceiving the filtered liquid mixture from the filter and for providingthe filtered liquid mixture to the measurement cell; pressure meanscoupled to at least the first chamber or at least the second chamber forforcing the liquid mixture through the filter by changing pressurerespectively within the first chamber or the second chamber; wherein thefiltration system is oriented in a substantially vertical position andincludes a first trough shaped bottom section forming a portion of thefirst chamber and a second trough shaped bottom section forming aportion of the second chamber.
 2. The filtration system of claim 1,wherein the pressure means comprises an air source coupled to at leastthe first chamber or at least the second chamber for forcing the liquidmixture through the filter by increasing pressure respectively withinthe first chamber or the second chamber.
 3. The filtration system ofclaim 2, wherein the second chamber is further coupled to a drain forreleasing draining excess filtrate from the second chamber.
 4. Thefiltration system of claim 1, wherein the pressure means is coupled toat least the second chamber and forces the liquid mixture through thefilter by creating a vacuum within the second chamber.
 5. The filtrationsystem of claim 4, wherein the second chamber is further coupled to avent line for venting the second chamber to atmospheric pressure.
 6. Thefiltration system of claim 1, wherein the first chamber is furthercoupled to a drain for releasing unfiltered liquid mixture from a bottomof the first chamber.
 7. The filtration system of claim 1, wherein themeasurement cell comprises a light source and one or more opticaldetectors for measuring one or more of: an attenuation of lightgenerated by the light source and passing through the filtered liquidmixture or a reflection spectrum of light generated by the light sourceand passing through the liquid mixture.
 8. The filtration system ofclaim 1, further comprising a computer control system for: controllingflow of the liquid mixture from the mixing chamber into the firstchamber; pressurizing the liquid mixture in the first chamber; andcontrolling flow of the filtered liquid mixture through the measurementcell.
 9. The filtration system of claim 1, wherein the liquid mixturecomprises a portion of a soil sample mixed with an extractant.
 10. Thefiltration system of claim 1, wherein the first chamber or the secondchamber is coupled to a cleaning fluid container for supplying cleaningfluid.
 11. The filtration system of claim 10, wherein the pressure meansis additionally for creating alternating pressure differentials betweenthe first chamber and the second chamber to pass the cleaning fluidthrough the filter to dislodge particulate caught in the filter.
 12. Thefiltration system of claim 11, wherein the first chamber is coupled tothe cleaning fluid container.
 13. The filtration system of claim 11,wherein the second chamber is coupled to the cleaning fluid container.